How do fractures perish?

The safety, sustainability and efficiency of many geotechnical structures (e.g. geological disposal of hazardous waste, dikes, landfills) strongly rely on the performance of clays, which are used as natural or engineered barrier to limit fluid flow and pollutant transport. Accordingly, considerable research effort has been put into the study of crack initiation and propagation. However, laboratory and field tests have also shown that cracks and fractures in clays have the capacity to naturally close, and that the material can partially recover its intact properties. A property known as self-healing.
The fundamental mechanisms responsible for self-healing of clays are poorly understood. The phenomenon has been studied in the laboratory by indirectly studying the impact, i.e. flow through the material, or by imaging techniques with low resolution. Simple models can represent the laboratory results, but their upscaling (in time and space) to real field-scale conditions remains challenging.

The overall objective of my research proposal is to develop a novel hydro-mechanical model for self-healing of clays, based on newly-collected insights in the fundamental self-healing mechanisms.
I propose to use a combination of high spatial-resolution and near real-time imaging and experimental testing to track the state of an interface during the self-healing process. This information will be used to define relevant microstructural state variables and develop a mechanism-based hydro-mechanical model of the fracture This will be embedded within a damage – healing cohesive-zone framework, and validated against laboratory and field data.
This research will significantly enhance the understanding, characterisation and predicting capacity of the behaviour of self-healing of clay-based materials. It will also open the door to the development of new clay-based materials able to heal fissures developing in slopes, dikes, embankments and landfills, thereby improving the sustainability of geotechnical structures.